Method and apparatus for controlling internal combustion engine for automotive vehicle

ABSTRACT

An apparatus for controlling an internal combustion engine for a vehicle includes a driving condition detecting unit (1-13, 50, 72) detecting a driving condition of the internal combustion engine and outputting a driving condition value indicative of the driving condition, and a control unit (71). The control portion has an input circuit (116, 113, 119) inputting a driving condition value from the driving condition detecting unit, detecting the driving condition value and outputting as the driving condition detection value, a reference power source circuit (70) generating a reference voltage (Vcc) for operating the control apparatus (FIG. 2) on the basis of a battery voltage from a battery (50), and a unit (CPU 100) controlling the internal combustion engine on the basis of the driving condition detected value from the input circuit.

TECHNICAL FIELD

The present invention relates to a method and an apparatus forcontrolling an internal combustion engine for an automotive vehicle.More particularly, the invention relates to a method and apparatus forcontrolling an internal combustion engine for an automotive vehicle,which can detect driving condition of the internal combustion enginewith small fluctuation per vehicle, at high accuracy and low cost.

BACKGROUND ART

Conventionally, in a control apparatus of an internal combustion enginemounted on an automotive vehicle, as sensors for detecting drivingcondition, such as an intake air flow rate, a coolant temperature, athrottle valve angular position and the like of the internal combustionengine, an air flow sensor, a coolant temperature sensor, a throttleangle sensor and the like are provided, respectively. Outputs of thesesensors are input to an input circuit and converted into a digital databy an analog/digital (A/D) converter in the input circuit, andsubsequently, arithmetically processed by a microcomputer. On the basisof results of process, actuators, such as a fuel injection device, aspark ignition device and the like are controlled. In a control unit, areference power source circuit which generates a reference voltage to besupplied to the control unit on the basis of a battery voltage from abattery mounted on the vehicle, that is, a vehiclar battery, isprovided.

On the other hand, the reference power source circuit is designed togenerate a constant voltage irrespective of fluctuation of the batteryvoltage. However, the reference voltage generated by the reference powersource circuit fluctuates per control units due to fluctuation of valuesof circuit elements (e.g., resistance value, a value of capacitor andthe like) forming the reference power source circuit per the controlunits. When the reference voltage to be generated by the reference powersource circuit fluctuates per control unit, the output values of thesensors and output values of the A/D converter also fluctuate per thecontrol unit. The fluctuation of the output values of the A/D converterdue to fluctuation of the circuit elements of the reference power sourcecircuit is about ±5%.

On the other hand, due to the fluctuation of the values of the circuitelements forming the A/D converter in the input circuit, the outputvalue of the A/D converter also fluctuates per the control unit. Thefluctuation of the output value of the A/D converter due to fluctuationof the circuit elements of the A/D converter is about ±0.05%.

An output voltage of the vehicular battery is applied to the A/Dconverter after voltage division by a divider circuit in the inputcircuit, to detect an output voltage. In this case, since the values ofthe circuit elements (e.g. resistor and the like) forming the dividercircuit fluctuate per control unit, the output value of the dividercircuit also fluctuates per control unit. The fluctuation of the outputvalue of the A/D converter due to fluctuation of the circuit element ofthe divider circuit is about ±1%.

In order to avoid fluctuation of the circuit element, it becomespossible to enhance precision of the values of respective circuitelements by employing a method, such as a laser trimming and the like.In this case, a problem is encountered to rise a cost.

On the other hand, conventionally, an alternator for a vehicle, which isdriven and rotated by the internal combustion engine of the automotivevehicle to perform power generating operation, has been controlledtypically by a control unit called in general as an IC regulator. The ICregulator controls an output of the alternator at a predetermined levelwhile detecting the voltage of the vehicular battery which is charged bythe output of the alternator.

According to JP-B-1-39306 (Publication (1)), there is shown a system inwhich an amount of current flowing through an exciting coil of thegenerator is controlled depending upon driving condition by applying acontrol signal of a microcomputer to a switching means incorporated inthe generator via a signal line to thereby control ON and OFF operationof the switching means.

In the control unit of the vehicular generator disclosed in theforegoing publication (1), there are little proposal for improvement ingeneration voltage of the generator and control precision of thegeneration voltage. In general, fluctuation of the circuit element ofthe portion generating the reference voltage in the IC regulator can beeliminated by employing a method for the laser trimming or the like. Insuch a case, a problem is encountered to make the cost high.

Thus, there is no system to achieve both the improvement of precision ofoutput of the A/D converter serving as the detection value of thedriving condition and the low cost of the control unit.

DISCLOSURE OF INVENTION

Accordingly, it is an object of the present invention to provide amethod and an apparatus for controlling an internal combustion enginefor an automotive vehicle, which can detected a driving condition of theinternal combustion engine with small fluctuation per vehicle, highprecision and low cost.

In order to accomplish such an object, according to one aspect of theinvention, an apparatus for controlling an internal combustion enginefor a vehicle comprises: a driving condition detecting unit fordetecting a driving condition of the internal combustion engine andoutputting a driving condition value indicative of the drivingcondition; an input circuit inputting a driving condition value from thedriving condition value from the driving condition detecting unit,detecting the driving condition value and outputting as a drivingcondition detection value; a reference power source circuit generating areference voltage for operating the control apparatus on the basis of abattery voltage from a battery; a memory unit for storing a correctiondata for correcting an error of the driving condition detected valuedetected by the input circuit caused by at least one of an error of thereference voltage from the reference power source circuit and an errorof the output of the input circuit; a correcting unit for correcting thedriving condition detected value from the input circuit with thecorrection data stored in the memory unit to obtain a correct drivingcondition detected value; and a unit for controlling the internalcombustion engine on the basis of the correct driving condition detectedvalue thus obtained.

In one example of the present invention, the driving condition detectingunit, the input circuit, the reference power source circuit, the unitfor controlling the internal combustion engine and the unit for derivingthe correction data are provided in a control unit of thecontrolapparatus. The correction data is derived and stored in thememory before installation of the control unit on the vehicle.Subsequently, the control unit storing the correction data in the memorythereof is installed in the control apparatus.

According to one example, a driving condition detected value output fromthe input circuit by applying a reference value of the driving conditionto the input circuit is compared with the reference value of the drivingcondition, and the correction data is derived on the basis of the resultof comparison. Here, the reference value of the driving conditionindicates the driving condition detected value detected by the inputcircuit by applying the reference value of the driving condition to theinput circuit at least when no error is contained in the referencevoltage from the reference power source circuit for example.

According to one example of the invention, the input circuit includes avoltage dividing circuit dividing the driving condition value from thedriving condition detecting unit at a predetermined ratio and ananalog/digital converter converting the dividing condition value fromthe voltge dividing circuit into a digital value.

According to one example of the invention, the unit for deriving thecorrection value obtains the ratio between the driving conditiondetected value output from the input circuit and the predeterminedreference driving condition detected value, as the correction data. Inthis case, the correction unit obtains the correct driving conditiondetected value by multiplying the driving condition detected value fromthe input circuit by the correction data stored in the memory.

According to one example of the invention, the unit for deriving thecorrection data stores the driving condition detected value output fromthe input circuit in the memory as an intermediate parameter of thecorrection data before installation of the control unit on the vehicle,and derives the correction data from the intermediate parameter storedin the memory and the predetermined reference driving condition detectedvalue, after installation of the control unit on the vehicle.

According to one example of the invention, as the above-mentionedmemory, the memory to be electrically written-in, such as P-ROM,EEP-ROM, flush memory and like, is employed.

According to the present invention, since the output (driving conditiondetected value) from the input circuit is corrected using the correctiondata which is derived in advance per the control apparatus of theinternal combustion engine, the error of the output value (detectedvalue of the driving condition) of the input circuit due to fluctuationof respective circuit elements of the reference power source circuit andthe input circuit (voltage divider, A/D converter) can be corrected perthe control apparatus of the internal combustion engine. Accordingly, itbecomes possible to control the internal combustion engine on the basisof correct A/D converted value of the driving condition value, such asthe sensor output, the battery voltage and so forth. Furthermore, sincethe generation voltage of the alternator as one kind of the drivingcondition can be detected with higher precision, the generation voltageof the alternator can be controlled with high precision to permit higherprecision control of the generation voltage and following ability of thegeneration amount depending upon the driving condition of the internalcombustion engine and the electric load condition. Furthermore, itbecomes possible to improve driving performance of the internalcombustion engine and to reduce fuel consumption. Furthermore, itbecomes possible to improve control precision of the internal combustionengine for preventing fluctuation of revolution during an idlingcondition. In the present invention, error of the output value of theinput circuit due to fluctuation of respective circuit elements of thereference power source circuit and the input circuit (voltage dividerand A/D converter) per the control apparatus of the internal combustionengine in not corrected by enhancing precision of the values of thecircuit elements using the method of laser trimming or so forth as inthe prior art. Namely, in the present invention, the error of the outputvalue of the input circuit is corrected using the correction datapreliminarily derived per the control apparatus of the internalcombustion engine and stored in the memory. Therefore, the output valueof the input circuit can be detected with high precision at low cost.

Furthermore, in the present invention, the driving condition detectingunit, the input circuit, the reference power source circuit, the unitfor controlling the internal combustion engine and the unit for derivingthe correction data are provided in the control unit of the controlapparatus, then the correction data is derived and stored in the memorybefore the control unit is installed in the control apparatus, namelybefore mounting on the vehicle. Subsequently, the control unit storingthe correction data in the memory thereof is installed in the controlapparatus.

Namely, in the factory manufacturing the control unit, after assemblingof the control unit, the correction data may be derived per the controlunit to store in the memory of the control unit. Thereafter, the controlunit may be shipped. The control unit may be subsequently installed inthe control apparatus, namely on the vehicle. Thus, upon shipping of thecontrol unit, the error specific to respective control unit can becorrected per the control unit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an illustration showing one example of the overallconstruction of a control system of an internal combustion engine of anautomotive vehicle, to which the present invention is applied;

FIG. 2 is a block diagram showing a construction of one embodiment of acontrol apparatus of an internal combustion engine for an automotivevehicle according to the present invention;

FIG. 3 is a flowchart showing a process for controlling a drivingcurrent amount to a exciting coil of a generator depending upon adriving condition;

FIG. 4 is a block diagram showing the major part of the controlapparatus of FIG. 2;

FIG. 5 is a illustration of a construction of the major part of acontrol unit for explaining a process for deriving correction data of adriving condition detection data and storing the same beforeinstallation of the control unit in FIG. 2 on the vehicle;

FIG. 6 is a flowchart for explaining the process for deriving acorrection data of a driving condition detection value and a correctiondata of a battery voltage detection value;

FIG. 7 is a flowchart for explaining a process for correcting thedriving condition detection value on the basis of the correction data;and

FIG. 8 is a flowchart for explaining the process for correcting abattery voltage detection value on the basis of the correction data.

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of a method and an apparatus for controlling an internalcombustion engine for an automotive vehicle according to the presentinvention will be discussed hereinafter in detail with reference to theaccompanying drawings.

FIG. 1 is an illustration showing one example of the overallconstruction of a control system for the internal combustion engine forthe automotive vehicle, to which the present invention is applied. FIG.2 is a block diagram showing a construction of one embodiment of acontrol apparatus for the automotive internal combustion engineaccording to the present invention.

In FIG. 1, an internal combustion engine 65 which is mounted on avehicle, such as an automotive vehicle, for example, has an output shaftoutputting a rotational torque, i.e. a crankshaft 66. The crankshaft 66is mechanically coupled with a vehicular alternator 51 via a pulley anda belt.

On the other hand, the internal combustion engine 65 transmits itsrotational torque to a driving wheels via a transmission as in thegeneral vehicle.

As one example shown in FIG. 1, a so-called MPI (multi-cylinder fuelinjection) type four-cylinder internal combustion engine will beexplained.

Air is guided to an air flow meter 2 provided at the outlet portion ofan air cleaner 60. As the air flow meter 2, a hot-wire type air flowsensor is employed. The air enters into a collector 62 via a duct 61connected to the air clearer, a throttle body including a throttle valve40 associated with an accelerator pedal operated by a driver andcontrolling an air flow rate, and an ISC (idle speed control) valve 41provided bypassing the throttle body and controlling an idling speed.Here, the air is distributed to respective intake manifold 63 directlyconnected to the engine and then sucked into cylinders.

A fuel is sucked from a fuel tank 21 by a fuel pump 20, pressurized,regulated at a constant pressure by a pressure regulator 22 and injectedinto the intake manifold through injectors 23 provided in the intakemanifold 63.

From an air flow meter 2, a signal corresponding to an intake air flowrate is output. On the other hand, from a crank angle sensor 7 built-ina distributor 32, a pulse is output per every predetermined crankshaftangular displacement. These outputs are input to a control unit 71, inwhich a crank angle and an engine speed are calculated. Also, on thebasis of the intake air flow rate and the engine speed thus calculated,a basic pulse width TP corresponding to a charging efficiency isderived.

At the throttle valve 40, a throttle angle sensor 1 detecting a throttlevalve open angle is mounted. The output signal of this sensor is inputto the control unit 71 to thereby detect the open angle of the throttlevalve 40, a fully closed state thereof and an acceleration state or thelike.

At the internal combustion engine 65, a coolant temperature sensor 3 fordetecting a coolant temperature is mounted. An output signal of thissensor is input to the control unit 71, which in turn detects a warm-upcondition, increases a fuel injection amount, corrects a spark ignitiontiming, controls ON/OFF state of a radiator fan 75 and sets a targetspeed upon idling.

An O₂ sensor 8 as an air/fuel ratio sensor is mounted on an exhaust pipeof the engine and adapted to output a signal depending upon an oxygenconcentration of an exhaust gas. This signal is input to the controlunit 71, which in turn adjusts fuel injection pulse widths for injectors23-1 to 23-4 so that a mixture to be supplied to the engine will have atarget air to fuel ratio (A/F).

4 denotes a neutral switch of a gear, 5 denotes a vehicle speed sensor,30 denotes an ignitor, 31 denotes a spark ignition coil, 33 denotes aspark plug, 73 denotes a lighting system including a headlamps.

As shown in FIG. 2, the control unit 71 is constructed with a CPU 100 asan arithmetic device, a ROM 101 as a read-only memory, a RAM 102 as amemory to be read out and written in, a back-up RAM 111 which does notclear the storage content thereof even when an ignition switch is turnedoff, an electrically writable memory 112 (for example, P-ROM, EEP-ROM,flash ROM or the like, here is assumed as EEP-ROM), an interruptcontroller 104, a timer 105, an input processing circuit 106 and anoutput processing circuit 107. These components are connected oneanother by a bus 108. The CPU 100 performs processes, based on theprogram stored in the ROM 101, on the basis of various informationprocessed by the input processing circuit by using the RAM 102 and theback-up RAM 111 which can hold the storage content thereof even duringOFF state of the ignition key 72. At this time, an interrupt process isperformed occasionally in response to an interrupt command generated byan interrupt controller 104 on the basis of the information from thetimer 105 and the input processing circuit 106.

A generation system will be explained. The alternator 51 is constructedwith a rotor on the outer periphery of which an exciting coil 54 iswound like the conventional alternator, and a stator around whichthree-phase windings 53a, 53b and 53c are wound so as to oppose to theouter perithery of the rotor. The rotor is rotatingly driven insynchronism with the crankshaft 66 of the internal combustion engine 65.A rectifier circuit 55 formed by series-parallel connected six diodes,for example, is connected to the three-phase windings 53a, 53b and 53cof the alternator 51, so that a three phase alternating output of thealternator 51 is rectified and supplied to the vehicular battery 50 forcharging the same. In the foregoing control unit 71, an alternatorcontrol program, for adjusting an output voltage of the alternator sothat the battery voltage becomes close to a target generation voltage,is incorporated. An exciting coil driving circuit 56 (for example,transistor) for controlling a control amount of the exciting coil 54,namely a driving amount (driving current) for the exciting coil 54, iscontrolled in the following manner. Namely, the CPU 100 compares avoltage 50a of the battery 50 which is charged by a generated power ofthe alternator 51 and detected by a voltage detection unit, i.e. theinput processing circuit 106, and a result of calculation of a targetgeneration voltage calculated depending upon a coolant temperaturerepresentative of a driving condition of the internal combustion engine.Then, the CPU calculates a driving amount of the exciting coil 54 sothat the voltage of the battery becomes close to the target voltagebased on the comparison result, and outputs the drive signal from thealternator control terminal (CL terminal) 51a to the exciting coildriving circuit 56. The revolution speed of the internal combustionengine is controlled by an ISC valve driving amount which is derived byadding an electric load correction amount derived from the drivingamount of the exciting coil and the driving condition to the drivingamount of the ISC valve 41.

The control apparatus of FIG. 2 controls respective actuators (the fuelinjectors 23-1 to 23-4, ISC valve 41, exciting circuit driving circuit56 and the like) on the basis of the values (namely, respectivedetection values of the driving condition of the internal combustionengine) of the output of various sensors taken by the input processingcircuit.

Next, in the control apparatus shown in FIG. 2, one example of processfor controlling the internal combustion engine depending upon thedriving condition of the internal combustion engine will be explainedwith reference to FIG. 3. FIG. 3 is a flowchart showing a process forcontrolling a driving current amount for the exciting coil of thealternator depending upon the driving condition. Here, explanation willbe given for the case where the output of the coolant temperature sensor3, namely the detection value of the coolant temperature is employed asthe driving condition. It should be noted that the process of FIG. 2 isexecuted by the CPU 100 on the basis of the program in the ROM 101.

At first, at step 220, the output signal of the coolant temperaturesensor 3 is read via the input processing circuit 106 and the bus 108 todetect the coolant temperature TWN. Next, at step 221, with reference toa table in the ROM 101 showing a relationship between a coolanttemperature TWN and a target generation voltage VBSET, a targetgeneration voltage VBSET is calculated on the basis of the detectedvalue of the coolant temperature TWN.

Next, at step 222, the battery voltage 50a from the battery 50 is readvia the input processing circuit 106 and the bus 108 to detect a batteryvoltage VB. At step 223, a voltage error ΔVB (=VBSET-VB) of the batteryvoltage detection value VB versus the target generation voltage VBSET iscalculated. At step 224, with reference to a table in the ROM 101showing a relationship between the voltage error ΔVB and the drivingamount of the exciting coil 54, a driving amount ALTDTY of the excitingcoil 54 is derived. As the driving amount of the exciting coil, a dutyratio of the pulse width of the drive signal to the transistor 56forming the exciting circuit driving circuit, for example, may beemployed.

Accordingly, by applying the drive signal having the duty ratioaccording to the driving amount ALTDTY of the derived exciting coil, tothe transistor 56 via the generator control terminal 51a from the outputprocessing circuit 107, the exciting current to the exciting coil 54 iscontrolled so that the battery voltage VB is controlled to be equal tothe target generation voltage VBSET.

Control of other actuators depending upon the driving condition isperformed in the similar manner.

FIG. 4 is a block diagram showing the construction of the major part ofthe control apparatus of FIG. 2. FIG. 4 shows the condition where thecontrol unit 71 is installed on the vehicle. As shown in FIG. 4, thecontrol unit 71 includes a reference power source circuit 71 generatinga reference voltage Vcc to be supplied to the control apparatus (controlunit 71, various sensor and the like) on the basis of the batteryvoltage 50a from the vehicular battery 50. The control unit 71 includesa voltage dividing circuit 119 for lowering the battery voltage 50athrough voltage division thereof so as to detect the battery voltage50a. The voltage dividing circuit 119 is included in the inputprocessing circuit 106. Also, the control unit 71 includes a transistor115 amplifying the drive signal from the CPU 100 for controlling thedriving current amount to the exciting coil 54 of the alternator and atransistor 114 amplifying the drive signal from the CPU 100 for drivinga charge lamp 76. These transistors 114 and 115 are included in theoutput processing circuit 107. The control unit 71 includes terminals116, 118, 120, LMP and CL. The output of the transistor 114 is appliedto the charge lamp 76 through the terminal LMP, while the output of thetransistor 115 is applied to the transistor 56 via the terminal CL. Theterminal 116 is a terminal for inputting the battery voltage 50a. Theterminal 118 is a terminal for inputting the output signal from the airflow sensor 2. The terminal 120 is a terminal for inputting an outputsignal of a knock sensor 13. While FIG. 4 shows only a part of varioussensors shown in FIG. 2, the outputs of other sensors are input to thecontrol unit 71 via the terminals of the control unit 71 in the samemanner. Although the control unit 71 includes the ROM 101 and so forthas shown in FIG. 2, they are omitted in FIG. 4.

As shown in FIG. 4, outputs from various sensors, such as the air flowsensor 2, the throttle angle sensor 1, the coolant temperature sensor,the knock sensor 13 and so forth, are applied to the A/D converter 113in the CPU 100 via the input processing circuit 106 and converted intodigital data. Since the battery voltage 50a from the vehicular battery50 is normally at a value of about 14.4 V, it is applied to the A/Dconverter 113 after voltage division by the voltage divider 119 forlowering down to the voltage value to be processed by the CPU 100.Typically, the battery voltage 50a is divided into one quarter by thevoltage divider 119.

As set forth above, since the reference power source circuit 70 hasfluctuation in value of the circuit elements (e.g. values of theresistor, capacitor, and the like) forming the same per the controlsystem, namely per the vehicle, the reference voltage Vcc generated bythe reference power source circuit 70 fluctuates per the controlapparatus. If the reference voltage generated by such a reference powersource circuit fluctuates per the control apparatus, the output valuesof the sensors and the output values of the A/D converter should alsofluctuate The fluctuation of the output value of the A/D converter dueto fluctuation of the circuit elements of the reference power sourcecircuit is about ±5%.

Also, since the values of the circuit elements forming the A/D converter100 in the CPU also fluctuates per the control apparatus, the outputvalue of the A/D converter should also fluctuates per the controlapparatus. The fluctuation of the output value of the A/D converter dueto fluctuation of the circuit elements of the A/D converter is about±0.05%.

Furthermore, the voltage divider circuit performing voltage division ofthe battery voltage also contains fluctuation of the values of thecircuit elements forming the same per the control apparatus. Therefore,the output value of the voltage divider circuit should also fluctuatesper the control apparatus. The fluctuation of the output value of theA/D converter due to fluctuation of the circuit elements of the voltagedivider is about ±1%.

Accordingly, error should be caused in the output value of the voltagedivider 119 and error should also be caused in the output value of theA/D converter 113 to make it impossible to accurately detect the outputvalues of the respective sensors and the battery voltage VB, namelydriving condition of the internal combustion engine. As a result, byfailure of accurate control depending upon the driving condition of theinternal combustion engine, degradation of fuel economy, lowering ofengine driving performance and so forth should be caused.

Therefore, in this embodiment, in order to correct error of the outputvalues (detection values of the driving condition) of the A/D converter113 due to fluctuation in the reference power source circuit 70, thevoltage divider circuit 119 and the A/D converter 113 per the controlapparatus, correction data for correcting the detection value of thedriving condition output from the A/D converter to a correct value(correct detection value of the driving condition) is derived in advanceper each control apparatus and stored in the memory of the correspondingcontrol apparatus. Then, the detection value of the driving conditionfrom the A/D converter is corrected to the correct value on the basis ofthe correction data stored in the memory.

FIG. 5 is a block diagram showing the configuration of the major part ofthe control unit 71 for performing the process to derive such correctiondata, and shows a status of the control unit before installation on thevehicle. The CPU 100 has "a correction data setting mode" for performinga process to derive the correction data and a normal "internalcombustion engine control mode" for controlling the internal combustionengine depending upon the driving condition. In order to perform theswitching between these two modes, the control unit 71 has a switch 130for commanding the switching between the "correction data setting mode"and the "internal combustion engine control mode", as shown in FIG. 5.One terminal of this switch 130 is grounded, and the other terminalthereof is connected to the CPU 100 via a terminal 124. When the switch130 is turned ON, the terminal 124 is grounded, then the CPU 100 isswitched into the "correction data setting mode", for example, and whenthe switch 120 is turned OFF, the CPU is switched into the "internalcombustion engine control mode". Accordingly, after termination of theprocess in the "correction data setting mode", the switch 130 is turnedOFF, and the control unit is installed with maintaining the OFF state ofthis switch.

It should be noted that, instead of providing the switch 124, anexternal communication unit 132 may be connected to a terminal 122 onlywhen the CPU 100 is to be operated in the "correction data settingmode". Namely, upon placing the CPU 100 in the "correction data settingmode", the external communication unit 122 may be connected to theterminal 122 to apply a predetermined signal from the externalcommunication unit 122 to the CPU 100 via the terminal 122 to place theCPU 100 in the "correction value setting mode".

A battery reference voltage generator 134 is connected to the terminals121 and 116. Thus, the battery reference voltage (e.g. 14.4 V) isapplied to the reference power source circuit 70 and the voltagedividing circuit 119. Also, a driving condition reference valuegenerator 136 is connected to one of a plurality of terminals providedin the control unit 71 for inputting the outputs from the varioussensors, for example, to the terminal 118 for inputting the output ofthe air flow sensor 2. The driving condition reference value generator136 outputs a driving condition reference value OCref (for example, thepredetermined voltage value, e.g. 4 V) as the reference value showingthe driving condition. In such a condition, the process to derive thecorrection data is performed.

FIG. 6 is a flowchart for explaining the process for deriving thecorrection data (correction coefficient, correction value or the like).This flowchart illustrates a process for deriving the correction data(correction coefficient, correction value or the like) with respect tothe output value of the A/D converter 113 in the case where the outputvalues from the various sensors are detected (measured) by the A/Dconverter 113 without passing through the voltage divider, and a processfor deriving the correction data for the output value of the A/Dconverter 113 in the case where the battery voltage is detected via thevoltage divider circuit 119 and the A/D converter 113. Here, explanationwill be made for the case where the correction data is derived on thebasis of the output of the air flow sensor 2. The processes shown inFIG. 6 and FIGS. 7 and 8 which will be discussed later, are executed bythe CPU 100 on the basis of the program in the ROM 101.

At first, at step 300, it is determined whether a level at the terminal124 of the control unit 71 is the ground level or not, namely, whetherthe operation mode of the CPU 100 is the "correction data setting mode"or the "internal combustion engine control mode". Namely, when theswitch 130 is turned ON and the level of the terminal 124 is thegrounding level, determination is made that the operation mode is the"correction value setting mode" and the process proceeds to step 302. Onthe other hand, when the switching 130 is turned OFF and the level ofthe terminal 124 is not the ground level, determination is made that theoperation mode is the "internal combustion engine control mode" toterminate the process.

At step 302, the driving condition reference value OCref (4 V) from thedriving condition reference value generator 136 is measured (detected)by the A/D converter 113 to obtain the A/D converted value (namely, thedetected value or the measured value of the driving condition referencevalue) OVADJ (e.g. 3.2 V) of the driving condition reference value.Next, at step 304, a ratio between the A/D converted value OVADJ of thedriving condition reference value and the correct A/D converted valueOCref of the driving condition reference value stored in the RAM 102,for example, in advance (namely, an ideal (true) A/D converted value ofthe driving condition reference value derived arithmetically in the casewhere it is assumed that no error of reference power source circuit 70and the A/D converter 113 is present, here 4 V) is derived. Namely,OCref÷OCADJ=correction coefficient OCCOR (here 4÷3.2=1.25) is obtained.Namely, this correction coefficient is the correction data forcorrecting the A/D converted value (detected value) OCAD value of thedriving condition to the true A/D converted value (detection value)OCADrel of the driving condition.

Next, at step 306, the derived correction coefficient OCCOR is stored inthe EEP-ROM 112.

The correction coefficient OCCOR thus derived can be used as thecorrection coefficient for other sensors other than the air flow sensor.The reason is that the A/D converter and the reference power sourcecircuit 70 are used in common for the various sensors.

It should be noted that, in this embodiment, the correction data withrespect to certain one sensor (namely certain one driving condition) isused as common correction data for all of the sensors (namely, all otherdriving conditions except for the battery voltage). However, it is alsopossible to individually derive the correction data (correctioncoefficients) with respect to respective kinds of sensors (namely,various driving conditions).

Upon shipping the control unit 71, the A/D converted value OCADJ of thedriving condition reference value per se may be stored in the EEP-ROM112 as the intermediate parameter. Then, after installation of thecontrol unit 71 on the vehicle, the OCADJ may be processed by thesimilar step as the step 304 to derive the correction coefficient OCCORby the CPU 100.

Next, the process for deriving the correction data with respect to thebattery voltage detection value by the A/D converter 113, will beexplained. At first, at step 308 after completion of step 306, thebattery reference voltage (14.4 V) from the battery reference voltagegenerator 134 is divided (here divided into one quarter) by the voltagedivider 119, and the divided voltage is measured (detected) by the A/Dconverter 113, thereby obtaining the A/D converted value (namely, thedetection value or the measured value of the battery reference voltage)VBADJ of the battery reference voltage (e.g. 3.2 V). Next, at step 310,the correct A/D converted value (VB reference value) after voltagedivision of the battery reference voltage (namely, the arithmeticallyderived ideal (true) A/D converted value of the battery referencevoltage in the case where it is assumed that no error is caused in thereference power source circuit 70, the voltage divider 119 and the A/Dconverter 113, here 14.4÷4=3.6 V) is derived.

Next, at step 312, a ratio between the A/D converted value VBADJ of thebattery reference voltage and the VB reference value is obtained.Namely, VB reference value VBADJ=correction coefficient VBOCR (here,3.6÷3.2=1.125) is obtained. Namely, the correction coefficient is thecorrection data for correcting the A/D converted value (detected value)VBAD value of the battery voltage 50a to the true A/D converted value(detected value) VBADrel) of the battery voltage.

Next, at step 314, the derived correction coefficient VBCOR is stored inthe EEP-ROM 112.

It should be noted that, upon shifting of the control unit 71, the A/Dconverted value VBADJ of the battery reference voltage per se may bestored in the EEP-ROM 112 as the intermediate parameter. Then, afterinstallation of the control unit 71 to the vehicle, VBADJ may beprocessed in the similar manner as the foregoing steps 310 and 312 toobtain the correction coefficient VBCOR by the CPU 100.

After storing the correction coefficient by the process shown in FIG. 6,the battery reference voltage generator 134, the driving conditionreference value generator 136 (and the external communication unit) areremoved away from the control unit 71. Subsequently, the control unit 71is installed on the vehicle to establish connected condition asillustrated in FIG. 4. It should be noted that the switch 130 is in anOFF state in this case.

FIG. 7 is a flowchart for explaining the process for obtaining theoutput values (correct A/D converted values, namely correct drivingcondition detection values) of the correct A/D converter 113 bycorrecting the output values of the A/D converter 113, when the outputvalues from the various sensors are detected (measured) by the A/Dconverter 113, on the basis of the correction data (correctioncoefficient) OCCOR obtained in the aforesaid manner.

At first, at step 400, A/D conversion is performed by taking the output(driving condition value) from the sensor (for example, the air flowsensor) in the A/D converter 113, to obtain the A/D converted value(detected value) OCAD of the driving condition. At step 402, thecorrection coefficient OCCOR is read out from the EEP-ROM 112. Next, atstep 404, the A/D converted value (detected value) OCAD of the drivingcondition obtained at step 400 is multiplied with the correctioncoefficient OCCOR obtained at step 402. Then, the obtained multipliedvalue is taken as the true (correct) A/D converted value (detectedvalue), OCAD true value (OCADrel) of the driving condition.

Thus, the true (correct) A/D converted value of the driving conditionwhere the error of the output value (driving condition detected value)of the A/D converter 113 due to fluctuation of the reference powersource circuit 70, the voltage divider 119 and the A/D converter 113 percontrol apparatus of the internal combustion engine, can be obtained.Accordingly, by controlling the internal combustion engine on the basisof the obtained correct A/D converted value of the driving condition,improvement of driving performance of the internal combustion engine andreduction of fuel consumption becomes possible. Furthermore, it becomespossible to improve precision in control of the internal combustionengine for preventing fluctuation of revolution -during an idling state.

FIG. 8 is a flowchart for explaining a process for correcting thedetected value of the battery voltage on the basis of the correctiondata and controlling the battery voltage on the basis of the correctbattery voltage having been corrected.

At first, at step 500, the battery voltage 50a of the battery 50 istaken into the A/D converter 113 via the voltage divider 119 to performA/D conversion to obtain the A/D converted value (detected value) VBADof the battery voltage. At step 502, the correction coefficient VBCOR isread out from the EEP-ROM 112. Next, at step 504, the A/D convertedvalue (detected value) VBAD of the battery voltage obtained at step 500is multiplied by the correction coefficient VBCOR obtained at step 502.The obtained multiplied value is taken as the true (correct) A/Dconverted value (detected value) of the battery voltage, VBCAD truevalue (VBADrel). Next, at step 506, by multiplying a dividingcoefficient 4 in the correct A/D converted value VBADrel of the batteryvoltage, true (correct) battery voltage VBrel is obtained.

Thus, the correct battery voltage, in which the error of the outputvalue (detected value of the driving condition) of the A/D converter 113due to fluctuation of the reference power source circuit 70, the voltagedivider 119 and the A/D converter 113, is corrected, can be obtained.For example, assuming that the reference power source voltage Vcc fromthe reference power source circuit 70 is in a precision of 5 V±0.25 V,namely having fluctuation of 0.5%, the detected value of the batteryvoltage should have error of 5%×4=20% due to the voltage dividingcoefficient 4 of the voltage dividing circuit 119. However, byperforming correction of the A/D converted value like this embodiment,it becomes possible to detect the battery voltage with high precisionwithout causing any fluctuation.

Next, the driving current amount for the exciting coil of the alternatoris controlled depending upon the driving condition on the basis of thethus obtained correct battery voltage and the detection value of thedriving condition in the similar process as shown in FIG. 3. At step508, by the similar process to FIG. 7, the correct A/D converted valueOCADrel of the driving condition (here, the driving condition is theoutput of the coolant temperature sensor 3, namely the coolanttemperature) is obtained. Next, at step 510, with reference to the tablein the ROM 101 showing a relationship between the A/D converted valueOCADrel and the target generation voltage VBSET, the target generationvoltage VBSET is calculated on the basis of the OCADrel.

Next, at step 512, a voltage difference ΔVB (ΔVB=VBSET-VBrel) of thecorrect battery voltage VBrel obtained at step 506 versus the targetgeneration voltage VBSET is calculated. At step 514, with reference tothe table in the ROM 101 showing a relationship between the voltagedifference ΔVB and the driving amount of the exciting coil 54, anexciting coil driving amount ALTDTY is obtained. The driving amount ofthe exciting coil, for example, may be the duty ratio of the pulse widthof the driving signal to the transistor 56 forming the exciting circuitdriving circuit, for example.

Accordingly, by applying the driving signal having the duty ratioaccording to the exciting coil driving amount ALTDTY thus obtained tothe transistor 56 via the alternator control terminal 51a from theoutput processing circuit 107, the exciting current to the exciting coil54 is controlled. Thus, the battery voltage VBrel is controlled to beequal to the target generation voltage VBSET.

Thus, according to the present invention, since the output (detectionvalue of the driving condition) from the input circuit is corrected byusing the correction data obtained in advance per control apparatus ofthe internal combustion engine, the error of the output value (detectionvalue of the driving condition) of the A/D converter 113 due tofluctuation of respective circuit elements of the reference power sourcecircuit 70, the voltage divider 119 and the A/D converter 113 per thecontrol apparatus can be corrected. Accordingly, the internal combustionengine can be controlled on the basis of the corrected A/D convertedvalues of the driving condition values of the sensor outputs, thebattery voltage or the like. Furthermore, since the generation voltageof the alternator as one kind of the driving condition can be detectedwith higher precision, it becomes possible to control generation voltageand following ability of generation amount at high precision dependingupon the driving condition of the internal combustion engine and theelectric load condition. Furthermore, improvement of driving performanceof the internal combustion engine or reduction of fuel consumptionbecomes possible. Furthermore, in order to perform suppression offluctuation of revolution in an idling state, precision of control ofthe internal combustion engine can be improved. In the presentinvention, an error of the output value of the A/D converter 113 due tofluctuation of respective circuit elements of the reference power sourcecircuit 70, the voltage divider 119 and the A/D converter 113 per thecontrol apparatus of the engine, is not corrected by enhancing precisionof the values of the circuit elements employing a method, such as lasertrimming or the like, as in the prior art. Namely, in the presentinvention, the error of the output value of the A/D converter iscorrected using the correction data obtained in advance per the controlapparatus of the internal combustion engine and stored in the memory.Therefore, the output value of the A/D converter 113 can be detectedwith high precision at low cost.

The foregoing embodiment uses a ratio between one reference value of acertain driving condition (for example, air flow rate detected by theair flow sensor) and an output value obtained by applying the referencevalue to the input circuit at the corresponding driving condition (theA/D converted value (detected value) of the reference value of thedriving condition), namely the correction coefficient as the correctiondata. However, it is possible to employ the following method as othermethod for deriving the correction data. Namely, a relationship betweenmutually different two reference values in a certain driving condition(for example, the air flow rate detected by the air flow sensor) and twooutput values obtained by applying the two reference values to the inputcircuit (the A/D converted values (detected values) of the referencevalue of the driving condition), is derived as a function, for exampleas a primary derivative function (a primary regression curve), andstored in the memory 112. Then, for detected value of the drivingcondition from the input circuit, the correct detected value of thedriving condition may be obtained using the foregoing function.

Furthermore, as a further method for deriving the correction data, thefollowing method may be employed. Namely, a difference between onereference value of a certain driving condition (for example, air flowrate detected by the air flow sensor) and an output value obtained byapplying the reference value to the input value at the correspondingdriving condition (the A/D converted value (detected value) of thereference value of the driving condition), can be taken as thecorrection data. In this case, by adding the difference (correctiondata) thus obtained to the A/D detected value of the driving condition,the correct A/D converted value may be obtained. Concerning the batteryvoltage, the corrected battery voltage can be obtained in the similarmanner.

INDUSTRIAL APPLICABILITY

As set forth above, the control method and the control system for theinternal combustion engine, according to the present invention areuseful for the control apparatus which controls the internal combustionengine on the basis of the driving condition values, such as sensoroutputs, battery voltage and so forth. Particularly, it is suitable toapply the present invention to the control apparatus which comprises theinput circuit inputting the driving condition value and outputting thedigital values thereof, and the reference power source circuit forgenerating reference voltage for operating the control apparatus on thebasis of the battery voltage from the vehicular battery, wherein thecircuit elements of the input circuit and the reference power sourcecircuit having fluctuation.

We claim:
 1. An apparatus for controlling an internal combustion enginefor a vehicle comprising:driving condition detecting means for detectinga driving condition of said internal combustion engine and outputting adriving condition value indicative of the driving condition; an inputcircuit inputting a driving condition value from the driving conditionvalue from said driving condition detecting means, detecting saiddriving condition value and outputting as a driving condition detectionvalue; a reference power source circuit generating a reference voltagefor operating said control apparatus on the basis of a battery voltagefrom a battery; memory means for storing a correction data forcorrecting an error of the driving condition detected value detected bysaid input circuit caused by at least one of an error of the referencevoltage from said reference power source circuit and an error of theoutput of said input circuit; correcting means for correcting thedriving condition detected value from said input circuit with saidcorrection data stored in said memory means to obtain a correct drivingcondition detected value; and means for controlling said internalcombustion engine on the basis of the correct driving condition detectedvalue thus obtained.
 2. A control apparatus as set forth in claim 1,which further comprises:means for obtaining said correction data; andmeans for storing the obtained correction data in said memory means. 3.A control apparatus as set forth in claim 2, which furthercomprises:means for selectively placing said means for obtaining saidcorrection data and said means for storing, in an operating condition.4. A control apparatus as set forth in claim 2, wherein said means forobtaining said correction data includesmeans for deriving saidcorrection data by comparing a driving condition detected value outputfrom said input circuit by applying a reference value of the drivingcondition to said input circuit with said reference value of saiddriving condition, and deriving said correction data on the basis of aresult of the comparison, wherein said reference value of the drivingcondition indicates the driving condition detected value detected bysaid input circuit by applying said reference value of said drivingcondition to said input circuit at least when no error is contained inthe reference voltage from said reference power source circuit.
 5. Acontrol apparatus as set forth in claim 2, wherein said means forderiving said correction value includesmeans for comparing the drivingcondition detected value output from said input circuit by applying thereference value of the driving condition to said input circuit and saidreference value of said driving condition, and means for deriving saidcorrection data on the basis of a result of comparison of said comparingmeans, wherein said reference value of the driving condition indicatesthe driving condition detected value detected by said input circuit byapplying said reference value of said driving condition to said inputcircuit at least when no error is contained in the reference voltagefrom said reference power source circuit.
 6. A control apparatus as setforth in claim 5, wherein said input circuit includes an analog/digitalconverter converting the driving condition value from said drivingcondition detecting means into a digital value.
 7. A control apparatusas set forth in claim 5, wherein said input circuit includes a voltagedivider dividing the driving condition value from said driving conditiondetecting means at a predetermined ratio and an analog/digital converterconverting the driving condition value from said voltage divider into adigital value.
 8. A control apparatus as set forth in claim 4, whereinsaid means for deriving said correction value includesmeans forobtaining a ratio between the driving condition detected value outputfrom said input circuit and said predetermined reference drivingcondition detected value, as said correction data.
 9. A controlapparatus as set forth in claim 1, said memory means is a memory whichcan be electrically written in.
 10. A method for controlling an internalcombustion engine for a vehicle in a control apparatus whichincludes:driving condition detecting means for detecting a drivingcondition of said internal combustion engine and outputting a drivingcondition value indicative of the driving condition; and a control unithaving an input circuit inputting a driving condition value from thedriving condition value from said driving condition detecting means,detecting said driving condition value and outputting as the drivingcondition detection value, a reference power source circuit generating areference voltage for operating said control apparatus on the basis of abattery voltage from a battery, and means for controlling said internalcombustion engine on the basis of a driving condition detected valuefrom said input circuit, wherein the control method by said control unitcomprising the steps of: a) storing a correction data for correction anerror of said driving condition detected value detected by said inputcircuit on the basis of at least one of an error of said referencevoltage from said reference power source circuit and an error of theoutput of said input circuit, in a memory means in said control unit; b)obtaining a correct driving condition detected value by correcting saiddriving condition detected value from said input circuit with thecorrection data stored in said memory means; and c) controlling saidinternal combustion engine on the basis of the obtained correct drivingcondition detected value.
 11. A control method as set forth in claim 10,which further comprises:d) step of deriving said correction data; and e)step of storing said derived correction data in said memory means.
 12. Acontrol method as set forth in claim 11, wherein said step of derivingsaid correction data and said step of storing are performed beforeinstalling said control unit on the vehicle.
 13. A control method as setforth in claim 11, wherein said step of deriving said correction datacomprises:step of comparing a driving condition detected value outputfrom said input circuit by applying a reference value of the drivingcondition to said input circuit with said reference value of saiddriving condition, and driving said correction data on the basis of aresult of the comparison, wherein said reference value of the drivingcondition indicates the driving condition detected value detected bysaid input circuit by applying said reference value of said drivingcondition to said input circuit at least when no error is contained inthe reference voltage from said reference power source circuit.
 14. Acontrol method as set forth in claim 11, wherein said step of derivingsaid correction data comprises:step of comparing the driving conditiondetected value output from said input circuit by applying a referencevalue of the driving condition to said input circuit and said referencevalue of said driving condition, and step of driving said correctiondata on the basis of a result of the comparison, wherein said referencevalue of the driving condition indicates the driving condition detectedvalue detected by said input circuit by applying said reference value ofsaid driving condition to said input circuit at least when no error iscontained in the reference voltage from said reference power sourcecircuit.
 15. A control method as set forth in claim 14, which furthercomprises a step of converting the driving condition value from saiddriving condition detecting means into digital value by a digital/analogconverter of said input circuit to output as said driving conditiondetected value.
 16. A control method as set forth in claim 14, whichfurther comprises a step of performing voltage division for said drivingcondition value from said driving condition detecting means at apredetermined ratio by a voltage divider circuit, and converting theoutput of said voltage divider circuit into digital value by ananalog/digital converter for outputting as said driving conditiondetected value.
 17. A control method as set forth in claim 13, whereinsaid step of deriving the correction data comprises a step of deriving aratio between the driving condition detected value output from saidinput circuit and said predetermined reference driving conditiondetected value, and obtaining said ratio as said correction data.
 18. Acontrol method as set forth in claim 17, wherein said step of obtainingsaid correct driving condition detected value obtains the correcteddriving condition detection value by multiplying the driving conditiondetected value from said input circuit by said correction data stored insaid memory means.
 19. A control method as set forth in claim 13,wherein said step of deriving said correction data comprises:step ofstoring the driving condition detected value output from said inputcircuit in said memory means as an intermediate parameter of saidcorrection data before installation of said control section on thevehicle; and step of deriving said correction data from saidintermediate parameter stored in said memory means and saidpredetermined reference driving condition detected value afterinstallation of said control section on the vehicle.
 20. A controlmethod as set forth in claim 10, wherein said step of storing in saidmemory means stores in said memory means which can be electricallywritten in.